/*
 * Copyright (c) 1991, 1992 Paul Kranenburg <pk@cs.few.eur.nl>
 * Copyright (c) 1993 Branko Lankester <branko@hacktic.nl>
 * Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <jrs@world.std.com>
 * Copyright (c) 1996-1999 Wichert Akkerman <wichert@cistron.nl>
 * Copyright (c) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *                     Linux for s390 port by D.J. Barrow
 *                    <barrow_dj@mail.yahoo.com,djbarrow@de.ibm.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "defs.h"
#include "dbg.h"
#include <sys/user.h>
#include <sys/stat.h>
#include <sys/param.h>
#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <openssl/md5.h>

#if HAVE_SYS_UIO_H
# include <sys/uio.h>
#endif

#if __GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 1)
# include <linux/ptrace.h>
#endif

#if defined(IA64)
# include <asm/ptrace_offsets.h>
# include <asm/rse.h>
#endif

#ifdef HAVE_SYS_REG_H
# include <sys/reg.h>
# define PTRACE_PEEKUSR PTRACE_PEEKUSER
#elif defined(HAVE_LINUX_PTRACE_H)
# undef PTRACE_SYSCALL
# ifdef HAVE_STRUCT_IA64_FPREG
#  define ia64_fpreg XXX_ia64_fpreg
# endif
# ifdef HAVE_STRUCT_PT_ALL_USER_REGS
#  define pt_all_user_regs XXX_pt_all_user_regs
# endif
# include <linux/ptrace.h>
# undef ia64_fpreg
# undef pt_all_user_regs
#endif

#if defined(SPARC64)
# undef PTRACE_GETREGS
# define PTRACE_GETREGS PTRACE_GETREGS64
# undef PTRACE_SETREGS
# define PTRACE_SETREGS PTRACE_SETREGS64
#endif

/* macros */
#ifndef MAX
# define MAX(a,b)       (((a) > (b)) ? (a) : (b))
#endif
#ifndef MIN
# define MIN(a,b)       (((a) < (b)) ? (a) : (b))
#endif

int
string_to_uint(const char *str)
{
    char *error;
    long value;

    if (!*str)
        return -1;
    errno = 0;
    value = strtol(str, &error, 10);
    if (errno || *error || value < 0 || (long)(int)value != value)
        return -1;
    return (int)value;
}

int
tv_nz(struct timeval *a)
{
    return a->tv_sec || a->tv_usec;
}

int
tv_cmp(struct timeval *a, struct timeval *b)
{
    if (a->tv_sec < b->tv_sec
        || (a->tv_sec == b->tv_sec && a->tv_usec < b->tv_usec))
        return -1;
    if (a->tv_sec > b->tv_sec
        || (a->tv_sec == b->tv_sec && a->tv_usec > b->tv_usec))
        return 1;
    return 0;
}

double
tv_float(struct timeval *tv)
{
    return tv->tv_sec + tv->tv_usec/1000000.0;
}

void
tv_add(struct timeval *tv, struct timeval *a, struct timeval *b)
{
    tv->tv_sec = a->tv_sec + b->tv_sec;
    tv->tv_usec = a->tv_usec + b->tv_usec;
    if (tv->tv_usec >= 1000000) {
        tv->tv_sec++;
        tv->tv_usec -= 1000000;
    }
}

void
tv_sub(struct timeval *tv, struct timeval *a, struct timeval *b)
{
    tv->tv_sec = a->tv_sec - b->tv_sec;
    tv->tv_usec = a->tv_usec - b->tv_usec;
    if (((long) tv->tv_usec) < 0) {
        tv->tv_sec--;
        tv->tv_usec += 1000000;
    }
}

void
tv_div(struct timeval *tv, struct timeval *a, int n)
{
    tv->tv_usec = (a->tv_sec % n * 1000000 + a->tv_usec + n / 2) / n;
    tv->tv_sec = a->tv_sec / n + tv->tv_usec / 1000000;
    tv->tv_usec %= 1000000;
}

void
tv_mul(struct timeval *tv, struct timeval *a, int n)
{
    tv->tv_usec = a->tv_usec * n;
    tv->tv_sec = a->tv_sec * n + tv->tv_usec / 1000000;
    tv->tv_usec %= 1000000;
}

const char *
xlookup(const struct xlat *xlat, int val)
{
    for (; xlat->str != NULL; xlat++)
        if (xlat->val == val)
            return xlat->str;
    return NULL;
}

#if !defined HAVE_STPCPY
char *
stpcpy(char *dst, const char *src)
{
    while ((*dst = *src++) != '\0')
        dst++;
    return dst;
}
#endif

/*
 * Print entry in struct xlat table, if there.
 */
void
printxval(const struct xlat *xlat, int val, const char *dflt)
{
    const char *str = xlookup(xlat, val);

    if (str)
        tprints(str);
    else
        tprintf("%#x /* %s */", val, dflt);
}

#if HAVE_LONG_LONG
/*
 * Print 64bit argument at position llarg and return the index of the next
 * argument.
 */
int
printllval(struct tcb *tcp, const char *format, int llarg)
{
# if defined(X86_64) || defined(POWERPC64)
    if (current_personality == 0) {
        tprintf(format, tcp->u_arg[llarg]);
        llarg++;
    } else {
#  ifdef POWERPC64
        /* Align 64bit argument to 64bit boundary.  */
        llarg = (llarg + 1) & 0x1e;
#  endif
        tprintf(format, LONG_LONG(tcp->u_arg[llarg], tcp->u_arg[llarg + 1]));
        llarg += 2;
    }
# elif defined IA64 || defined ALPHA
    tprintf(format, tcp->u_arg[llarg]);
    llarg++;
# elif defined LINUX_MIPSN32 || defined X32
    tprintf(format, tcp->ext_arg[llarg]);
    llarg++;
# else
    tprintf(format, LONG_LONG(tcp->u_arg[llarg], tcp->u_arg[llarg + 1]));
    llarg += 2;
# endif
    return llarg;
}
#endif

/*
 * Interpret `xlat' as an array of flags
 * print the entries whose bits are on in `flags'
 * return # of flags printed.
 */
void
addflags(const struct xlat *xlat, int flags)
{
    for (; xlat->str; xlat++) {
        if (xlat->val && (flags & xlat->val) == xlat->val) {
            tprintf("|%s", xlat->str);
            flags &= ~xlat->val;
        }
    }
    if (flags) {
        tprintf("|%#x", flags);
    }
}

/*
 * Interpret `xlat' as an array of flags.
 * Print to static string the entries whose bits are on in `flags'
 * Return static string.
 */
const char *
sprintflags(const char *prefix, const struct xlat *xlat, int flags)
{
    static char outstr[1024];
    char *outptr;
    int found = 0;

    outptr = stpcpy(outstr, prefix);

    for (; xlat->str; xlat++) {
        if ((flags & xlat->val) == xlat->val) {
            if (found)
                *outptr++ = '|';
            outptr = stpcpy(outptr, xlat->str);
            found = 1;
            flags &= ~xlat->val;
            if (!flags)
                break;
        }
    }
    if (flags) {
        if (found)
            *outptr++ = '|';
        outptr += sprintf(outptr, "%#x", flags);
    }

    return outstr;
}

int
printflags(const struct xlat *xlat, int flags, const char *dflt)
{
    int n;
    const char *sep;

    if (flags == 0 && xlat->val == 0) {
        tprints(xlat->str);
        return 1;
    }

    sep = "";
    for (n = 0; xlat->str; xlat++) {
        if (xlat->val && (flags & xlat->val) == xlat->val) {
            tprintf("%s%s", sep, xlat->str);
            flags &= ~xlat->val;
            sep = "|";
            n++;
        }
    }

    if (n) {
        if (flags) {
            tprintf("%s%#x", sep, flags);
            n++;
        }
    } else {
        if (flags) {
            tprintf("%#x", flags);
            if (dflt)
                tprintf(" /* %s */", dflt);
        } else {
            if (dflt)
                tprints("0");
        }
    }

    return n;
}

void
printnum(struct tcb *tcp, long addr, const char *fmt)
{
    long num;

    if (!addr) {
        tprints("NULL");
        return;
    }
    if (umove(tcp, addr, &num) < 0) {
        tprintf("%#lx", addr);
        return;
    }
    tprints("[");
    tprintf(fmt, num);
    tprints("]");
}

void
printnum_int(struct tcb *tcp, long addr, const char *fmt)
{
    int num;

    if (!addr) {
        tprints("NULL");
        return;
    }
    if (umove(tcp, addr, &num) < 0) {
        tprintf("%#lx", addr);
        return;
    }
    tprints("[");
    tprintf(fmt, num);
    tprints("]");
}

void
printfd(struct tcb *tcp, int fd)
{
    const char *p;

    if (show_fd_path && (p = getfdpath(tcp, fd)))
        tprintf("%d<%s>", fd, p);
    else
        tprintf("%d", fd);
}

void
printuid(const char *text, unsigned long uid)
{
    tprintf((uid == -1) ? "%s%ld" : "%s%lu", text, uid);
}

/*
 * Quote string `instr' of length `size'
 * Write up to (3 + `size' * 4) bytes to `outstr' buffer.
 * If `len' is -1, treat `instr' as a NUL-terminated string
 * and quote at most (`size' - 1) bytes.
 *
 * Returns 0 if len == -1 and NUL was seen, 1 otherwise.
 * Note that if len >= 0, always returns 1.
 */
int
string_quote(const char *instr, char *outstr, long len, int size)
{
    const unsigned char *ustr = (const unsigned char *) instr;
    char *s = outstr;
    int usehex, c, i, eol;

    eol = 0x100; /* this can never match a char */
    if (len == -1) {
        size--;
        eol = '\0';
    }

    usehex = 0;
    if (xflag > 1)
        usehex = 1;
    else if (xflag) {
        /* Check for presence of symbol which require
           to hex-quote the whole string. */
        for (i = 0; i < size; ++i) {
            c = ustr[i];
            /* Check for NUL-terminated string. */
            if (c == eol)
                break;
            if (!isprint(c) && !isspace(c)) {
                usehex = 1;
                break;
            }
        }
    }

    *s++ = '\"';

    if (usehex) {
        /* Hex-quote the whole string. */
        for (i = 0; i < size; ++i) {
            c = ustr[i];
            /* Check for NUL-terminated string. */
            if (c == eol)
                goto asciz_ended;
            *s++ = '\\';
            *s++ = 'x';
            *s++ = "0123456789abcdef"[c >> 4];
            *s++ = "0123456789abcdef"[c & 0xf];
        }
    } else {
        for (i = 0; i < size; ++i) {
            c = ustr[i];
            /* Check for NUL-terminated string. */
            if (c == eol)
                goto asciz_ended;
            switch (c) {
                case '\"': case '\\':
                    *s++ = '\\';
                    *s++ = c;
                    break;
                case '\f':
                    *s++ = '\\';
                    *s++ = 'f';
                    break;
                case '\n':
                    *s++ = '\\';
                    *s++ = 'n';
                    break;
                case '\r':
                    *s++ = '\\';
                    *s++ = 'r';
                    break;
                case '\t':
                    *s++ = '\\';
                    *s++ = 't';
                    break;
                case '\v':
                    *s++ = '\\';
                    *s++ = 'v';
                    break;
                default:
                    if (isprint(c))
                        *s++ = c;
                    else {
                        /* Print \octal */
                        *s++ = '\\';
                        if (i + 1 < size
                            && ustr[i + 1] >= '0'
                            && ustr[i + 1] <= '9'
                        ) {
                            /* Print \ooo */
                            *s++ = '0' + (c >> 6);
                            *s++ = '0' + ((c >> 3) & 0x7);
                        } else {
                            /* Print \[[o]o]o */
                            if ((c >> 3) != 0) {
                                if ((c >> 6) != 0)
                                    *s++ = '0' + (c >> 6);
                                *s++ = '0' + ((c >> 3) & 0x7);
                            }
                        }
                        *s++ = '0' + (c & 0x7);
                    }
                    break;
            }
        }
    }

    *s++ = '\"';
    *s = '\0';

    /* Return zero if we printed entire ASCIZ string (didn't truncate it) */
    if (len == -1 && ustr[i] == '\0') {
        /* We didn't see NUL yet (otherwise we'd jump to 'asciz_ended')
         * but next char is NUL.
         */
        return 0;
    }

    return 1;

 asciz_ended:
    *s++ = '\"';
    *s = '\0';
    /* Return zero: we printed entire ASCIZ string (didn't truncate it) */
    return 0;
}

/*
 * Print path string specified by address `addr' and length `n'.
 * If path length exceeds `n', append `...' to the output.
 */
void
printpathn(struct tcb *tcp, long addr, int n)
{
    char path[MAXPATHLEN + 1];
    int nul_seen;

    if (!addr) {
        tprints("NULL");
        return;
    }

    /* Cap path length to the path buffer size */
    if (n > sizeof path - 1)
        n = sizeof path - 1;

    /* Fetch one byte more to find out whether path length > n. */
    nul_seen = umovestr(tcp, addr, n + 1, path);
    if (nul_seen < 0)
        tprintf("%#lx", addr);
    else {
        char *outstr;

        path[n] = '\0';
        n++;
        outstr = alloca(4 * n); /* 4*(n-1) + 3 for quotes and NUL */
        string_quote(path, outstr, -1, n);
        tprints(outstr);
        if (!nul_seen)
            tprints("...");
    }
}

void
printpath(struct tcb *tcp, long addr)
{
    /* Size must correspond to char path[] size in printpathn */
    printpathn(tcp, addr, MAXPATHLEN);
}

/*
 * Print string specified by address `addr' and length `len'.
 * If `len' < 0, treat the string as a NUL-terminated string.
 * If string length exceeds `max_strlen', append `...' to the output.
 */
void
printstr(struct tcb *tcp, long addr, long len)
{
    static char *str = NULL;
    static char *outstr;
    int size;
    int ellipsis;

    if (!addr) {
        tprints("NULL");
        return;
    }
    /* Allocate static buffers if they are not allocated yet. */
    if (!str) {
        unsigned int outstr_size = 4 * max_strlen + /*for quotes and NUL:*/ 3;

        if (outstr_size / 4 != max_strlen)
            die_out_of_memory();
        str = malloc(max_strlen + 1);
        if (!str)
            die_out_of_memory();
        outstr = malloc(outstr_size);
        if (!outstr)
            die_out_of_memory();
    }

    if (len == -1) {
        /*
         * Treat as a NUL-terminated string: fetch one byte more
         * because string_quote() quotes one byte less.
         */
        size = max_strlen + 1;
        if (umovestr(tcp, addr, size, str) < 0) {
            tprintf("%#lx", addr);
            return;
        }
    }
    else {
        size = max_strlen;
        if (size > (unsigned long)len)
            size = (unsigned long)len;
        if (umoven(tcp, addr, size, str) < 0) {
            tprintf("%#lx", addr);
            return;
        }
    }

    /* If string_quote didn't see NUL and (it was supposed to be ASCIZ str
     * or we were requested to print more than -s NUM chars)...
     */
    ellipsis = (string_quote(str, outstr, len, size) &&
            (len < 0 || len > max_strlen));

    tprints(outstr);
    if (ellipsis)
        tprints("...");
}

#if HAVE_SYS_UIO_H
void
dumpiov(struct tcb *tcp, int len, long addr)
{
#if SUPPORTED_PERSONALITIES > 1
    union {
        struct { u_int32_t base; u_int32_t len; } *iov32;
        struct { u_int64_t base; u_int64_t len; } *iov64;
    } iovu;
#define iov iovu.iov64
#define sizeof_iov \
    (current_wordsize == 4 ? sizeof(*iovu.iov32) : sizeof(*iovu.iov64))
#define iov_iov_base(i) \
    (current_wordsize == 4 ? (uint64_t) iovu.iov32[i].base : iovu.iov64[i].base)
#define iov_iov_len(i) \
    (current_wordsize == 4 ? (uint64_t) iovu.iov32[i].len : iovu.iov64[i].len)
#else
    struct iovec *iov;
#define sizeof_iov sizeof(*iov)
#define iov_iov_base(i) iov[i].iov_base
#define iov_iov_len(i) iov[i].iov_len
#endif
    int i;
    unsigned size;

    size = sizeof_iov * len;
    /* Assuming no sane program has millions of iovs */
    if ((unsigned)len > 1024*1024 /* insane or negative size? */
        || (iov = malloc(size)) == NULL) {
        fprintf(stderr, "Out of memory\n");
        return;
    }
    if (umoven(tcp, addr, size, (char *) iov) >= 0) {
        for (i = 0; i < len; i++) {
            /* include the buffer number to make it easy to
             * match up the trace with the source */
            tprintf(" * %lu bytes in buffer %d\n",
                (unsigned long)iov_iov_len(i), i);
            dumpstr(tcp, (long) iov_iov_base(i),
                iov_iov_len(i));
        }
    }
    free(iov);
#undef sizeof_iov
#undef iov_iov_base
#undef iov_iov_len
#undef iov
}
#endif

void
dumpstr(struct tcb *tcp, long addr, int len)
{
    static int strsize = -1;
    static unsigned char *str;
    char *s;
    int i, j;

    if (strsize < len) {
        free(str);
        str = malloc(len);
        if (!str) {
            strsize = -1;
            fprintf(stderr, "Out of memory\n");
            return;
        }
        strsize = len;
    }

    if (umoven(tcp, addr, len, (char *) str) < 0)
        return;

    for (i = 0; i < len; i += 16) {
        char outstr[80];

        s = outstr;
        sprintf(s, " | %05x ", i);
        s += 9;
        for (j = 0; j < 16; j++) {
            if (j == 8)
                *s++ = ' ';
            if (i + j < len) {
                sprintf(s, " %02x", str[i + j]);
                s += 3;
            }
            else {
                *s++ = ' '; *s++ = ' '; *s++ = ' ';
            }
        }
        *s++ = ' '; *s++ = ' ';
        for (j = 0; j < 16; j++) {
            if (j == 8)
                *s++ = ' ';
            if (i + j < len) {
                if (isprint(str[i + j]))
                    *s++ = str[i + j];
                else
                    *s++ = '.';
            }
            else
                *s++ = ' ';
        }
        tprintf("%s |\n", outstr);
    }
}

#ifdef HAVE_PROCESS_VM_READV
/* C library supports this, but the kernel might not. */
static bool process_vm_readv_not_supported = 0;
#else

/* Need to do this since process_vm_readv() is not yet available in libc.
 * When libc is be updated, only "static bool process_vm_readv_not_supported"
 * line should remain.
 */
#if !defined(__NR_process_vm_readv)
# if defined(I386)
#  define __NR_process_vm_readv  347
# elif defined(X86_64)
#  define __NR_process_vm_readv  310
# elif defined(POWERPC)
#  define __NR_process_vm_readv  351
# endif
#endif

#if defined(__NR_process_vm_readv)
static bool process_vm_readv_not_supported = 0;
static ssize_t process_vm_readv(pid_t pid,
         const struct iovec *lvec,
         unsigned long liovcnt,
         const struct iovec *rvec,
         unsigned long riovcnt,
         unsigned long flags)
{
    return syscall(__NR_process_vm_readv, (long)pid, lvec, liovcnt, rvec, riovcnt, flags);
}
#else
static bool process_vm_readv_not_supported = 1;
# define process_vm_readv(...) (errno = ENOSYS, -1)
#endif

#endif /* end of hack */

#define PAGMASK (~(PAGSIZ - 1))
/*
 * move `len' bytes of data from process `pid'
 * at address `addr' to our space at `laddr'
 */
int
umoven(struct tcb *tcp, long addr, int len, char *laddr)
{
    int pid = tcp->pid;
    int n, m;
    int started;
    union {
        long val;
        char x[sizeof(long)];
    } u;

#if SUPPORTED_PERSONALITIES > 1
    if (current_wordsize < sizeof(addr))
        addr &= (1ul << 8 * current_wordsize) - 1;
#endif

    if (!process_vm_readv_not_supported) {
        struct iovec local[1], remote[1];
        int r;

        local[0].iov_base = laddr;
        remote[0].iov_base = (void*)addr;
        local[0].iov_len = remote[0].iov_len = len;
        r = process_vm_readv(pid,
                local, 1,
                remote, 1,
                /*flags:*/ 0
        );
        if (r < 0) {
            if (errno == ENOSYS)
                process_vm_readv_not_supported = 1;
            else if (errno != EINVAL) /* EINVAL is seen if process is gone */
                /* strange... */
                perror("process_vm_readv");
            goto vm_readv_didnt_work;
        }
        return r;
    }
 vm_readv_didnt_work:

    started = 0;
    if (addr & (sizeof(long) - 1)) {
        /* addr not a multiple of sizeof(long) */
        n = addr - (addr & -sizeof(long)); /* residue */
        addr &= -sizeof(long); /* residue */
        errno = 0;
        u.val = ptrace(PTRACE_PEEKDATA, pid, (char *) addr, 0);
        if (errno) {
            /* But if not started, we had a bogus address. */
            if (addr != 0 && errno != EIO && errno != ESRCH)
                perror_msg("umoven: PTRACE_PEEKDATA pid:%d @0x%lx", pid, addr);
            return -1;
        }
        started = 1;
        m = MIN(sizeof(long) - n, len);
        memcpy(laddr, &u.x[n], m);
        addr += sizeof(long), laddr += m, len -= m;
    }
    while (len) {
        errno = 0;
        u.val = ptrace(PTRACE_PEEKDATA, pid, (char *) addr, 0);
        if (errno) {
            if (started && (errno==EPERM || errno==EIO)) {
                /* Ran into 'end of memory' - stupid "printpath" */
                return 0;
            }
            if (addr != 0 && errno != EIO && errno != ESRCH)
                perror_msg("umoven: PTRACE_PEEKDATA pid:%d @0x%lx", pid, addr);
            return -1;
        }
        started = 1;
        m = MIN(sizeof(long), len);
        memcpy(laddr, u.x, m);
        addr += sizeof(long), laddr += m, len -= m;
    }

    return 0;
}

/*
 * Like `umove' but make the additional effort of looking
 * for a terminating zero byte.
 *
 * Returns < 0 on error, > 0 if NUL was seen,
 * (TODO if useful: return count of bytes including NUL),
 * else 0 if len bytes were read but no NUL byte seen.
 *
 * Note: there is no guarantee we won't overwrite some bytes
 * in laddr[] _after_ terminating NUL (but, of course,
 * we never write past laddr[len-1]).
 */
int
umovestr(struct tcb *tcp, long addr, int len, char *laddr)
{
    int started;
    int pid = tcp->pid;
    int i, n, m;
    union {
        long val;
        char x[sizeof(long)];
    } u;

#if SUPPORTED_PERSONALITIES > 1
    if (current_wordsize < sizeof(addr))
        addr &= (1ul << 8 * current_wordsize) - 1;
#endif

    if (!process_vm_readv_not_supported) {
        struct iovec local[1], remote[1];

        local[0].iov_base = laddr;
        remote[0].iov_base = (void*)addr;

        while (len > 0) {
            int end_in_page;
            int r;
            int chunk_len;

            /* Don't read kilobytes: most strings are short */
            chunk_len = len;
            if (chunk_len > 256)
                chunk_len = 256;
            /* Don't cross pages. I guess otherwise we can get EFAULT
             * and fail to notice that terminating NUL lies
             * in the existing (first) page.
             * (I hope there aren't arches with pages < 4K)
             */
            end_in_page = ((addr + chunk_len) & 4095);
            r = chunk_len - end_in_page;
            if (r > 0) /* if chunk_len > end_in_page */
                chunk_len = r; /* chunk_len -= end_in_page */

            local[0].iov_len = remote[0].iov_len = chunk_len;
            r = process_vm_readv(pid,
                    local, 1,
                    remote, 1,
                    /*flags:*/ 0
            );
            if (r < 0) {
                if (errno == ENOSYS) {
                    process_vm_readv_not_supported = 1;
                }
                else if (errno != EINVAL) /* EINVAL is seen if process is gone */ {
                    /* strange... */
                    perror("process_vm_readv");
                }
                goto vm_readv_didnt_work;
            }
            if (memchr(local[0].iov_base, '\0', r))
                return 1;
            local[0].iov_base += r;
            remote[0].iov_base += r;
            len -= r;
        }
        return 0;
    }
 vm_readv_didnt_work:

    started = 0;
    if (addr & (sizeof(long) - 1)) {
        /* addr not a multiple of sizeof(long) */
        n = addr - (addr & -sizeof(long)); /* residue */
        addr &= -sizeof(long); /* residue */
        errno = 0;
        u.val = ptrace(PTRACE_PEEKDATA, pid, (char *)addr, 0);
        if (errno) {
            if (addr != 0 && errno != EIO && errno != ESRCH)
                perror_msg("umovestr: PTRACE_PEEKDATA pid:%d @0x%lx", pid, addr);
            return -1;
        }
        started = 1;
        m = MIN(sizeof(long) - n, len);
        memcpy(laddr, &u.x[n], m);
        while (n & (sizeof(long) - 1))
            if (u.x[n++] == '\0')
                return 1;
        addr += sizeof(long), laddr += m, len -= m;
    }
    while (len) {
        errno = 0;
        u.val = ptrace(PTRACE_PEEKDATA, pid, (char *)addr, 0);
        if (errno) {
            if (started && (errno==EPERM || errno==EIO)) {
                /* Ran into 'end of memory' - stupid "printpath" */
                return 0;
            }
            if (addr != 0 && errno != EIO && errno != ESRCH)
                perror_msg("umovestr: PTRACE_PEEKDATA pid:%d @0x%lx", pid, addr);
            return -1;
        }
        started = 1;
        m = MIN(sizeof(long), len);
        memcpy(laddr, u.x, m);
        for (i = 0; i < sizeof(long); i++)
            if (u.x[i] == '\0')
                return 1;
        addr += sizeof(long), laddr += m, len -= m;
    }
    return 0;
}

int
upeek(struct tcb *tcp, long off, long *res)
{
    long val;

    errno = 0;
    val = ptrace(PTRACE_PEEKUSER, tcp->pid, (char *) off, 0);
    if (val == -1 && errno) {
        if (errno != ESRCH) {
            perror_msg("upeek: PTRACE_PEEKUSER pid:%d @0x%lx)", tcp->pid, off);
        }
        return -1;
    }
    *res = val;
    return 0;
}

void
printcall(struct tcb *tcp)
{
#define PRINTBADPC tprints(sizeof(long) == 4 ? "[????????] " : \
               sizeof(long) == 8 ? "[????????????????] " : \
               NULL /* crash */)

#if defined(I386)
    long eip;

    if (upeek(tcp, 4*EIP, &eip) < 0) {
        PRINTBADPC;
        return;
    }
    tprintf("[%08lx] ", eip);
#elif defined(S390) || defined(S390X)
    long psw;
    if (upeek(tcp, PT_PSWADDR, &psw) < 0) {
        PRINTBADPC;
        return;
    }
# ifdef S390
    tprintf("[%08lx] ", psw);
# elif S390X
    tprintf("[%16lx] ", psw);
# endif

#elif defined(X86_64) || defined(X32)
    long rip;

    if (upeek(tcp, 8*RIP, &rip) < 0) {
        PRINTBADPC;
        return;
    }
    tprintf("[%16lx] ", rip);
#elif defined(IA64)
    long ip;

    if (upeek(tcp, PT_B0, &ip) < 0) {
        PRINTBADPC;
        return;
    }
    tprintf("[%08lx] ", ip);
#elif defined(POWERPC)
    long pc;

    if (upeek(tcp, sizeof(unsigned long)*PT_NIP, &pc) < 0) {
        PRINTBADPC;
        return;
    }
# ifdef POWERPC64
    tprintf("[%016lx] ", pc);
# else
    tprintf("[%08lx] ", pc);
# endif
#elif defined(M68K)
    long pc;

    if (upeek(tcp, 4*PT_PC, &pc) < 0) {
        tprints("[????????] ");
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(ALPHA)
    long pc;

    if (upeek(tcp, REG_PC, &pc) < 0) {
        tprints("[????????????????] ");
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(SPARC) || defined(SPARC64)
    struct pt_regs regs;
    if (ptrace(PTRACE_GETREGS, tcp->pid, (char *)&regs, 0) < 0) {
        PRINTBADPC;
        return;
    }
# if defined(SPARC64)
    tprintf("[%08lx] ", regs.tpc);
# else
    tprintf("[%08lx] ", regs.pc);
# endif
#elif defined(HPPA)
    long pc;

    if (upeek(tcp, PT_IAOQ0, &pc) < 0) {
        tprints("[????????] ");
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(MIPS)
    long pc;

    if (upeek(tcp, REG_EPC, &pc) < 0) {
        tprints("[????????] ");
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(SH)
    long pc;

    if (upeek(tcp, 4*REG_PC, &pc) < 0) {
        tprints("[????????] ");
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(SH64)
    long pc;

    if (upeek(tcp, REG_PC, &pc) < 0) {
        tprints("[????????????????] ");
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(ARM)
    long pc;

    if (upeek(tcp, 4*15, &pc) < 0) {
        PRINTBADPC;
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(AVR32)
    long pc;

    if (upeek(tcp, REG_PC, &pc) < 0) {
        tprints("[????????] ");
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(BFIN)
    long pc;

    if (upeek(tcp, PT_PC, &pc) < 0) {
        PRINTBADPC;
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(CRISV10)
    long pc;

    if (upeek(tcp, 4*PT_IRP, &pc) < 0) {
        PRINTBADPC;
        return;
    }
    tprintf("[%08lx] ", pc);
#elif defined(CRISV32)
    long pc;

    if (upeek(tcp, 4*PT_ERP, &pc) < 0) {
        PRINTBADPC;
        return;
    }
    tprintf("[%08lx] ", pc);
#endif /* architecture */
}

/*
 * These #if's are huge, please indent them correctly.
 * It's easy to get confused otherwise.
 */

#include "syscall.h"

#ifndef CLONE_PTRACE
# define CLONE_PTRACE    0x00002000
#endif
#ifndef CLONE_VFORK
# define CLONE_VFORK     0x00004000
#endif
#ifndef CLONE_VM
# define CLONE_VM        0x00000100
#endif

static int
change_syscall(struct tcb *tcp, int new)
{
#if defined(I386)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(ORIG_EAX * 4), new) < 0)
        return -1;
    return 0;
#elif defined(X86_64) || defined(X32)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(ORIG_RAX * 8), new) < 0)
        return -1;
    return 0;
#elif defined(POWERPC)
    if (ptrace(PTRACE_POKEUSER, tcp->pid,
           (char*)(sizeof(unsigned long)*PT_R0), new) < 0)
        return -1;
    return 0;
#elif defined(S390) || defined(S390X)
    /* s390 linux after 2.4.7 has a hook in entry.S to allow this */
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(PT_GPR2), new) < 0)
        return -1;
    return 0;
#elif defined(M68K)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(4*PT_ORIG_D0), new) < 0)
        return -1;
    return 0;
#elif defined(SPARC) || defined(SPARC64)
    struct pt_regs regs;
    if (ptrace(PTRACE_GETREGS, tcp->pid, (char*)&regs, 0) < 0)
        return -1;
    regs.u_regs[U_REG_G1] = new;
    if (ptrace(PTRACE_SETREGS, tcp->pid, (char*)&regs, 0) < 0)
        return -1;
    return 0;
#elif defined(MIPS)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(REG_V0), new) < 0)
        return -1;
    return 0;
#elif defined(ALPHA)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(REG_A3), new) < 0)
        return -1;
    return 0;
#elif defined(AVR32)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(REG_R8), new) < 0)
        return -1;
    return 0;
#elif defined(BFIN)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(REG_P0), new) < 0)
        return -1;
    return 0;
#elif defined(IA64)
    if (ia32) {
        switch (new) {
        case 2:
            break;  /* x86 SYS_fork */
        case SYS_clone:
            new = 120;
            break;
        default:
            fprintf(stderr, "%s: unexpected syscall %d\n",
                __FUNCTION__, new);
            return -1;
        }
        if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(PT_R1), new) < 0)
            return -1;
    } else if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(PT_R15), new) < 0)
        return -1;
    return 0;
#elif defined(HPPA)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(PT_GR20), new) < 0)
        return -1;
    return 0;
#elif defined(SH)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(4*(REG_REG0+3)), new) < 0)
        return -1;
    return 0;
#elif defined(SH64)
    /* Top half of reg encodes the no. of args n as 0x1n.
       Assume 0 args as kernel never actually checks... */
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(REG_SYSCALL),
                0x100000 | new) < 0)
        return -1;
    return 0;
#elif defined(CRISV10) || defined(CRISV32)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(4*PT_R9), new) < 0)
        return -1;
    return 0;
#elif defined(ARM)
    /* Some kernels support this, some (pre-2.6.16 or so) don't.  */
# ifndef PTRACE_SET_SYSCALL
#  define PTRACE_SET_SYSCALL 23
# endif
    if (ptrace(PTRACE_SET_SYSCALL, tcp->pid, 0, new & 0xffff) != 0)
        return -1;
    return 0;
#elif defined(TILE)
    if (ptrace(PTRACE_POKEUSER, tcp->pid,
           (char*)PTREGS_OFFSET_REG(0),
           new) != 0)
        return -1;
    return 0;
#elif defined(MICROBLAZE)
    if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(PT_GPR(0)), new) < 0)
        return -1;
    return 0;
#else
#warning Do not know how to handle change_syscall for this architecture
#endif /* architecture */
    return -1;
}

#ifdef IA64

typedef unsigned long *arg_setup_state;

static int
arg_setup(struct tcb *tcp, arg_setup_state *state)
{
    unsigned long cfm, sof, sol;
    long bsp;

    if (ia32) {
        /* Satisfy a false GCC warning.  */
        *state = NULL;
        return 0;
    }

    if (upeek(tcp, PT_AR_BSP, &bsp) < 0)
        return -1;
    if (upeek(tcp, PT_CFM, (long *) &cfm) < 0)
        return -1;

    sof = (cfm >> 0) & 0x7f;
    sol = (cfm >> 7) & 0x7f;
    bsp = (long) ia64_rse_skip_regs((unsigned long *) bsp, -sof + sol);

    *state = (unsigned long *) bsp;
    return 0;
}

# define arg_finish_change(tcp, state)  0

static int
get_arg0(struct tcb *tcp, arg_setup_state *state, long *valp)
{
    int ret;

    if (ia32)
        ret = upeek(tcp, PT_R11, valp);
    else
        ret = umoven(tcp,
                  (unsigned long) ia64_rse_skip_regs(*state, 0),
                  sizeof(long), (void *) valp);
    return ret;
}

static int
get_arg1(struct tcb *tcp, arg_setup_state *state, long *valp)
{
    int ret;

    if (ia32)
        ret = upeek(tcp, PT_R9, valp);
    else
        ret = umoven(tcp,
                  (unsigned long) ia64_rse_skip_regs(*state, 1),
                  sizeof(long), (void *) valp);
    return ret;
}

static int
set_arg0(struct tcb *tcp, arg_setup_state *state, long val)
{
    int req = PTRACE_POKEDATA;
    void *ap;

    if (ia32) {
        ap = (void *) (intptr_t) PT_R11;     /* r11 == EBX */
        req = PTRACE_POKEUSER;
    } else
        ap = ia64_rse_skip_regs(*state, 0);
    errno = 0;
    ptrace(req, tcp->pid, ap, val);
    return errno ? -1 : 0;
}

static int
set_arg1(struct tcb *tcp, arg_setup_state *state, long val)
{
    int req = PTRACE_POKEDATA;
    void *ap;

    if (ia32) {
        ap = (void *) (intptr_t) PT_R9;     /* r9 == ECX */
        req = PTRACE_POKEUSER;
    } else
        ap = ia64_rse_skip_regs(*state, 1);
    errno = 0;
    ptrace(req, tcp->pid, ap, val);
    return errno ? -1 : 0;
}

/* ia64 does not return the input arguments from functions (and syscalls)
   according to ia64 RSE (Register Stack Engine) behavior.  */

# define restore_arg0(tcp, state, val) ((void) (state), 0)
# define restore_arg1(tcp, state, val) ((void) (state), 0)

#elif defined(SPARC) || defined(SPARC64)

typedef struct pt_regs arg_setup_state;

# define arg_setup(tcp, state) \
    (ptrace(PTRACE_GETREGS, (tcp)->pid, (char *) (state), 0))
# define arg_finish_change(tcp, state) \
    (ptrace(PTRACE_SETREGS, (tcp)->pid, (char *) (state), 0))

# define get_arg0(tcp, state, valp) (*(valp) = (state)->u_regs[U_REG_O0], 0)
# define get_arg1(tcp, state, valp) (*(valp) = (state)->u_regs[U_REG_O1], 0)
# define set_arg0(tcp, state, val)  ((state)->u_regs[U_REG_O0] = (val), 0)
# define set_arg1(tcp, state, val)  ((state)->u_regs[U_REG_O1] = (val), 0)
# define restore_arg0(tcp, state, val) 0

#else /* other architectures */

# if defined S390 || defined S390X
/* Note: this is only true for the `clone' system call, which handles
   arguments specially.  We could as well say that its first two arguments
   are swapped relative to other architectures, but that would just be
   another #ifdef in the calls.  */
#  define arg0_offset   PT_GPR3
#  define arg1_offset   PT_ORIGGPR2
#  define restore_arg0(tcp, state, val) ((void) (state), 0)
#  define restore_arg1(tcp, state, val) ((void) (state), 0)
#  define arg0_index    1
#  define arg1_index    0
# elif defined(ALPHA) || defined(MIPS)
#  define arg0_offset   REG_A0
#  define arg1_offset   (REG_A0+1)
# elif defined(AVR32)
#  define arg0_offset   (REG_R12)
#  define arg1_offset   (REG_R11)
# elif defined(POWERPC)
#  define arg0_offset   (sizeof(unsigned long)*PT_R3)
#  define arg1_offset   (sizeof(unsigned long)*PT_R4)
#  define restore_arg0(tcp, state, val) ((void) (state), 0)
# elif defined(HPPA)
#  define arg0_offset   PT_GR26
#  define arg1_offset   (PT_GR26-4)
# elif defined(X86_64) || defined(X32)
#  define arg0_offset   ((long)(8*(current_personality ? RBX : RDI)))
#  define arg1_offset   ((long)(8*(current_personality ? RCX : RSI)))
# elif defined(SH)
#  define arg0_offset   (4*(REG_REG0+4))
#  define arg1_offset   (4*(REG_REG0+5))
# elif defined(SH64)
   /* ABI defines arg0 & 1 in r2 & r3 */
#  define arg0_offset   (REG_OFFSET+16)
#  define arg1_offset   (REG_OFFSET+24)
#  define restore_arg0(tcp, state, val) 0
# elif defined CRISV10 || defined CRISV32
#  define arg0_offset   (4*PT_R11)
#  define arg1_offset   (4*PT_ORIG_R10)
#  define restore_arg0(tcp, state, val) 0
#  define restore_arg1(tcp, state, val) 0
#  define arg0_index    1
#  define arg1_index    0
# else
#  define arg0_offset   0
#  define arg1_offset   4
#  if defined ARM
#   define restore_arg0(tcp, state, val) 0
#  endif
# endif

typedef int arg_setup_state;

# define arg_setup(tcp, state)         (0)
# define arg_finish_change(tcp, state) 0
# define get_arg0(tcp, cookie, valp)   (upeek((tcp), arg0_offset, (valp)))
# define get_arg1(tcp, cookie, valp)   (upeek((tcp), arg1_offset, (valp)))

static int
set_arg0(struct tcb *tcp, void *cookie, long val)
{
    return ptrace(PTRACE_POKEUSER, tcp->pid, (char*)arg0_offset, val);
}

static int
set_arg1(struct tcb *tcp, void *cookie, long val)
{
    return ptrace(PTRACE_POKEUSER, tcp->pid, (char*)arg1_offset, val);
}

#endif /* architectures */

#ifndef restore_arg0
# define restore_arg0(tcp, state, val) set_arg0((tcp), (state), (val))
#endif
#ifndef restore_arg1
# define restore_arg1(tcp, state, val) set_arg1((tcp), (state), (val))
#endif

#ifndef arg0_index
# define arg0_index 0
# define arg1_index 1
#endif

int
setbpt(struct tcb *tcp)
{
    static int clone_scno[SUPPORTED_PERSONALITIES] = { SYS_clone };
    arg_setup_state state;

    if (tcp->flags & TCB_BPTSET) {
        fprintf(stderr, "PANIC: TCB already set in pid %u\n", tcp->pid);
        return -1;
    }

    /*
     * It's a silly kludge to initialize this with a search at runtime.
     * But it's better than maintaining another magic thing in the
     * godforsaken tables.
     */
    if (clone_scno[current_personality] == 0) {
        int i;
        for (i = 0; i < nsyscalls; ++i)
            if (sysent[i].sys_func == sys_clone) {
                clone_scno[current_personality] = i;
                break;
            }
    }

    if (sysent[tcp->scno].sys_func == sys_fork ||
        sysent[tcp->scno].sys_func == sys_vfork) {
        if (arg_setup(tcp, &state) < 0
            || get_arg0(tcp, &state, &tcp->inst[0]) < 0
            || get_arg1(tcp, &state, &tcp->inst[1]) < 0
            || change_syscall(tcp, clone_scno[current_personality]) < 0
            || set_arg0(tcp, &state, CLONE_PTRACE|SIGCHLD) < 0
            || set_arg1(tcp, &state, 0) < 0
            || arg_finish_change(tcp, &state) < 0)
            return -1;
        tcp->u_arg[arg0_index] = CLONE_PTRACE|SIGCHLD;
        tcp->u_arg[arg1_index] = 0;
        tcp->flags |= TCB_BPTSET;
        return 0;
    }

    if (sysent[tcp->scno].sys_func == sys_clone) {
        /* ia64 calls directly `clone (CLONE_VFORK | CLONE_VM)'
           contrary to x86 vfork above.  Even on x86 we turn the
           vfork semantics into plain fork - each application must not
           depend on the vfork specifics according to POSIX.  We would
           hang waiting for the parent resume otherwise.  We need to
           clear also CLONE_VM but only in the CLONE_VFORK case as
           otherwise we would break pthread_create.  */

        long new_arg0 = (tcp->u_arg[arg0_index] | CLONE_PTRACE);
        if (new_arg0 & CLONE_VFORK)
            new_arg0 &= ~(unsigned long)(CLONE_VFORK | CLONE_VM);
        if (arg_setup(tcp, &state) < 0
         || set_arg0(tcp, &state, new_arg0) < 0
         || arg_finish_change(tcp, &state) < 0)
            return -1;
        tcp->flags |= TCB_BPTSET;
        tcp->inst[0] = tcp->u_arg[arg0_index];
        tcp->inst[1] = tcp->u_arg[arg1_index];
        return 0;
    }

    fprintf(stderr, "PANIC: setbpt for syscall %ld on %u???\n",
        tcp->scno, tcp->pid);
    return -1;
}

int
clearbpt(struct tcb *tcp)
{
    arg_setup_state state;
    if (arg_setup(tcp, &state) < 0
        || restore_arg0(tcp, &state, tcp->inst[0]) < 0
        || restore_arg1(tcp, &state, tcp->inst[1]) < 0
        || arg_finish_change(tcp, &state))
        if (errno != ESRCH)
            return -1;
    tcp->flags &= ~TCB_BPTSET;
    return 0;
}

int
mkdirp(char *pn, mode_t mode)
{
    int done = 0;
    int ret = 0;
    char *iter = pn;

    while (!done && *(++iter) != '\0') {
        // find next '/' or '\0'
        for (; *iter != '\0' && *iter != '/'; iter ++);

        // done
        if (*iter == '\0') {
            done = 1;
        }

        // make a dir
        *iter = '\0';
        ret = mkdir(pn, mode);
        if (done) {
            break;
        }

        // continue
        *iter = '/';
    }

    return ret == 0 || errno == EEXIST;
}

int
touch(char *dst, int mode) 
{
    int fd = open(dst, O_CREAT|O_WRONLY|O_TRUNC, mode);
    if (fd < 0) {
        perror("touch:");
        return 0;
    }
    close(fd);
    return 1;
}

int
copyfile(char *src, char *dst, byte *md5)
{
    struct stat src_stat;
    if (stat(src, &src_stat) < 0) {
        // fine if not exist
        return 0;
    }

    // NOTE. if src is symlink, we follow the link for now, but the correct
    // semantic might be clone the link to the dst

    // check if a regular file
    if (!S_ISREG(src_stat.st_mode)) {
        return 0;
    }
    
    int src_fd = open(src, O_RDONLY);
    if (src_fd < 0) {
        if (opt_fakeroot) {
            dbg(fakeroot, "touch %s (src is root only access)", dst);
            touch(dst, src_stat.st_mode);
        } else {
            dbg(info, "open src: %s (%s)", src, strerror(errno));
        }
        return 0;
    }

    int dst_fd = open(dst, O_CREAT|O_WRONLY|O_TRUNC, src_stat.st_mode);
    if (dst_fd < 0) {
        perror("open dst");
        close(src_fd);
        return 0;
    }

    MD5_CTX ctx;
    if (md5) {
        MD5_Init(&ctx);
    }
    
    char buf[PAGE_SIZE];
    
    int bytes;
    int ret = 1;
    while ((bytes = read(src_fd, buf, sizeof(buf))) > 0) {
        if (write(dst_fd, buf, bytes) != bytes) {
            perror("write:");
            ret = 0;
            break;
        }
        if (md5) {
            MD5_Update(&ctx, buf, bytes);
        }
    }

    close(src_fd);
    close(dst_fd);

    if (md5) {
        MD5_Final(md5, &ctx);
    }
    
    return ret;
}

int
exists_parent_dir(char *path) 
{
    char *iter = path + strlen(path);
    for (; iter >= path && *iter != '/' ; iter --);
    if (iter == path) {
        return 1;
    }

    int ret = 0;
    *iter = '\0';
    if (access(path, F_OK) == 0) {
        ret = 1;
    }
    *iter = '/';
    
    return ret;
}

char
kbhit(void)
{
    char c;
    
    struct termios oldt, newt;

    /*tcgetattr gets the parameters of the current terminal
      STDIN_FILENO will tell tcgetattr that it should write the settings
      of stdin to oldt*/
    tcgetattr(STDIN_FILENO, &oldt);
    /*now the settings will be copied*/
    newt = oldt;

    /*ICANON normally takes care that one line at a time will be processed
      that means it will return if it sees a "\n" or an EOF or an EOL*/
    newt.c_lflag &= ~(ICANON);

    /*Those new settings will be set to STDIN
      TCSANOW tells tcsetattr to change attributes immediately. */
    tcsetattr( STDIN_FILENO, TCSANOW, &newt);

    /*This is your part:
      I choose 'e' to end input. Notice that EOF is also turned off
      in the non-canonical mode*/
    c = getchar();

    /*restore the old settings*/
    tcsetattr( STDIN_FILENO, TCSANOW, &oldt);

    return c;
}

// name is \0 ended and abspath.
// name won't be overwritten longer than the given length.
int
normalize_path(char *name)
{
    char *iter = name;
    char *head = name;

    while (*iter != '\0') {
        // skip duplicated /
        while (*iter == '/') {
           iter ++;
        }

        // reaches to the end
        if (*iter == '\0') {
            break;
        }

        // handles ./ and ../
        if (*iter == '.') {
            char *next1 = iter + 1;
            char *next2 = iter + 2;

            if (*next1 == '\0' || *next1 == '/') {
                // ignore .
                iter += 2;

                // done
                if (*next1 == '\0') {
                    goto done;
                }

                // restart normalizing
                continue;
            } else if (*next1 == '.' && (*next2 == '\0' || *next2 == '/')) {
                // adjust head
                do {
                    head --;
                } while (*head != '/' && name != head);
                
                iter += 3;

                // done
                if (*next2 == '\0') {
                    goto done;
                }
                
                // restart normalizing
                continue;
            }
        }

        // single /
        *head = '/';
        head ++;

        while (*iter && *iter != '/') {
            *head = *iter;
            head ++;
            iter ++;
        }
    }

 done:
    // keep root
    if (head == name) {
        *head = '/';
        head ++;
    }

    *head = '\0';
    return 0;
}

int strbeg(const char *str, const char *prefix) {
    return strncmp(str, prefix, strlen(prefix)) == 0;
}